This invention relates to wireless networks generally and particularly to non-frequency-hopping nodes operating in a frequency-hopping system.
A wireless network is a flexible data communication medium implemented as an extension for, or as an alternative to, a wired network. By using radio frequency (RF) technology, wireless networks transmit and receive data over air, minimizing the need and the cost typically associated with wired connections. Moreover, wireless networks offer mobility and flexibility for users. For example, doctors and nurses in hospitals are able to use hand-held devices or notebook computers to access patient information from a server through wireless networks without having to search for a physical connection into which to plug.
Many wireless networks use spread-spectrum technology, a wideband radio frequency technique originally developed by the military for use in reliable, secure and mission-critical communication systems. Spread-spectrum is designed to trade off bandwidth efficiency for data reliability, integrity and security. One of the techniques for spread spectrum modulation is frequency-hopping spread-spectrum (FHSS). Specifically, FHSS uses a narrowband carrier that changes frequency in a pattern known to both a FHSS transmitter and a FHSS receiver. Because of this pattern of frequency changes or hops, to an unintended receiver, FHSS signals appear to be short-duration interference bursts.
In order to tune to the different frequency channels in the pattern of frequency changes, systems utilizing FESS employ some frequency switching components, such as pseudo-noise generator (or also known as pseudo-random sequence generator) and frequency synthesizers. Even though frequency synthesizers represent a significant portion of the overall system cost, they are necessary for full performance of the FHSS systems (or also referred to as frequency-hopping systems). Nevertheless, devices begin to emerge, such as devices designed for home use, where full performance of the frequency-hopping system is not required. For instance, a thermostat in a home may periodically transmit the home""s present in-door temperature through a wireless network to a server tracking conditions of this home. If this thermostat implements the described frequency synthesizer, the cost of the thermostat will most likely become prohibitively high in view of its functionality.
Therefore, in order to promote commercially viable wireless devices, which transmit relatively small amounts of information on an infrequent basis, a method is needed to produce such devices to operate in a frequency-hopping system.
A non-frequency-hopping node and a method for using such a node to transmit and receive data in a frequency-hopping system are disclosed.
In one embodiment, a non-frequency-hopping node interacts with a frequency-hopping spread-spectrum (FHSS) system, which comprises a wireless medium or electromagnetic airwaves, a frequency-hopping node coupled to the wireless medium and an access point coupled to the wireless medium. The non-frequency-hopping node connects to the wireless medium and listens for an active signal generated by the FHSS system on a predetermined frequency channel. Upon detecting the active signal, the non-frequency-hopping node exchanges information with the FHSS system on the predetermined frequency channel.